L-Tryptophan and Thiamine Hydrochloride as Vital Factors of the Indole Acetic Acid and Siderophores Produced by Rhizobium leguminosarum bv. viceae and Their reflection on Faba Bean growth Yield and some Soil Properties under Saline Soil

Abstract

Plant growth promoting rhizobacteria such as R. leguminosarum bv. viceae strains no. 481 & 441 were shown to produce indole-3-acetic acid (IAA) and siderophores in bacterial culture supplemented with L-tryptophan (L-trp) and thiamine hydrochloride (Thch) concentrations. Maximum IAA production was found in the medium amended with 1.5mg ml^-1 (L-trp). IAA production was not observed with the (L-trp) in free medium while (Thch) produced a maximum amount of growth and IAA at 3 mg ml^-1 for both the two rhizobial strains. Biosynthesis of siderophore was maximum (44.23% and 35.75%) at 1.5mg ml^-1 of (L-trp ) while the production of sidrophore was (40.49% & 34.68 % of siderophore units) at 3 mg ml^-1 of (Thch) in R. leguminosarum bv. viceae strain 481 & 441 respectively. Rhizobial strain 481 was more active in the production IAA and siderophore than the other rhizobial strain 441.

A field experiment on a newly reclaimed saline soil at Sahl El-Hussinia, El-Sharkia Governorate, Egypt, used to evaluate the effect of IAA and siderophores synthesizing by rhizobial strains on plant growth parameters and soil characteristics. The obtained results revealed that applying of rhizobial strains grown on 1.5mg ml^-1 L-Trp and 3 mg ml^-1 (Thch) led to improve soil properties which reflected on the crop growth and yield components. Soil respiration (CO₂ evolution) and proline content were also studied.